$100$g of benzene were spilled into a well that penetrates an aquifer in which

average ground water velocity is $10$ m$/$yr$.$ The aquifer is $5$ m deep. Your home$$s well is $200$ m downgradient of the well with the spill. Assume Dx$=200$ m$2/$y and Dy$=$Dz$=20$ m$2/$y$.$Assume the porosity is $0\mathrm{.}5$ and no sorption between benzene and aquifer solids.$($a$)$ When will maximum benzene concentrations occur at your well? Is the tracer well$-$mixed before it gets to your house?

$($b$)$ What will the maximum benzene concentration be at your well?

$($c$)$ At the time that you see maximum concentrations at your house, what will the

benzene concentration be at your neighbor$$s house located $20$ meters away?

$($d$)$ Compute how chemical reaction $($k$=0\mathrm{.}0005/$d$)$ will affect your answers to $($a$),($b$),$ and $($c$).$